Anti-biofilm Formation Activities of 4-hydroxyindole Azo Compounds against Pseudomonas aeruginosa and Staphylococcus aureus

A hybrid of six (6) 4-hydroxyindole azo compounds was synthesised by the diazotization and coupling strategy via electrophilic aromatic substitution reaction. Characterisation by Infrared and UV-Vis spectroscopic studies was carried out and the antimicrobial activity and structure-activity relationship were explored. Amongst the compounds, 4d was the most active against Pseudomonas aeruginosa than the other organisms from the high-throughput spot culture growth inhibition (HTSPOTi) antimicrobial assay. According to the resistant modulation study, the compounds did not show significant activity against the panel of pathogens used. Furthermore, compounds 4a and 4f inhibited biofilm formation in Pseudomonas aeruginosa and Staphylococcus aureus at 70% (31.25 µg/mL) and 57% (125 (µg/mL) respectively. Additionally, 4c and 4e have biofilm inhibition potential against Pseudomonas aeruginosa and Staphylococcus aureus which are implicated in antimicrobial resistance. Hence, the compounds are promising leads with potential to be developed into new antibacterial agents to combat the menace of antimicrobial resistance.